Generally, fired ceramics and other hard and/or thick materials may be machined using lasers. Other machining processes may also be used such as grinding or chemical etching. However, grinding and other mechanical processes provide limited machining resolution. Further, hard and abrasive materials such as fired ceramic wear down mechanical devices used during the machining process.
In addition to ceramics, other hard materials may include, but are not limited to, single crystal silicon, multicrystalline silicon, metal, glass, sapphire, and zirconium. When machining such materials, including fired ceramic, it is typically desirable to increase throughput and quality.
Ceramic is generally processed in either a green state or a fired state. In the green state, before the ceramic has been heated or baked, it is relatively soft and easy to process. However, the process of firing the ceramic tends to change or distort the dimensions of features initially machined in the green ceramic. Thus, when precise dimensions and geometries are desired for the end product, processing green ceramic before it is fired may not provide sufficient quality. Fired ceramic, however, is substantially harder than green ceramic and relatively more difficult to machine. Thus, throughput is generally lower when machining fired ceramic as compared to green ceramic.
When using a laser to machine fired ceramic, higher laser power may be used for faster processing. However, increasing laser power may result in the final product having a quality that is less than adequate. Known laser techniques may produce excessive heat and debris that may cause, for example, edge roughness and thermal damage.
As the material thickness and laser depth of focus increase, it is generally more difficult to achieve the throughput and quality desired. Debris from the laser machining process typically limits throughput and quality. For example, conventional laser cutting profiles may suffer from trench backfill of laser ejected material. When the material thickness is increased, this backfill becomes more severe and reduces machining efficiency. Further, for some materials under many process conditions, the ejected backfill material may be more difficult to remove on subsequent passes than the original target material. Thus, cuts of low quality are created that can damage the material and require additional cleaning.
Lowering laser power may be used to improve quality. However, using a lower laser power may result in reduced throughput.